In its first public criticism of the counter-terror bill, the association said exercising new powers to close places of worship where there were concerns about extremism could prove counter-productive. Rob Beckley, Hertfordshire assistant chief constable and the association spokesman on communities and terrorism, said: "We believe the police have to engage fully with communities to prevent extremism from becoming terrorism. We are concerned that a measure introduced to close a building related to a particular religion sends the wrong message to those communities and potentially prevents police from proper engagement and gaining vital intelligence.

"If we suspect there is extremism that is verging on promotion of terrorism in a mosque we wouldn't just want to close that mosque. We would want to find out what was happening."

Mr Beckley also cautioned against government plans to outlaw Hizb ut-Tahrir. "Banning any organisation must be a last resort, and it is our belief that a case must be made against an organisation itself rather than some members of it, before such a step is taken.

"They [Hizb ut-Tahrir] proclaim themselves to be against violence. What we need to do is test that but not automatically ban them because there are some radicals within their organisation, some individuals who we might be wanting to take action against or to look at very closely. What we don't want to do is drive extremism and radicalism, where it is not an offence, to drive that underground."

Senior police officers were accused of political meddling when Acpo lobbied for the government's proposal to allow police to hold terrorist suspects for 90 days without charge, although this was knocked back to 28 days after a revolt by Labour MPs. But Mr Beckley's comments come after the Guardian revealed last week that police chiefs were privately critical of four of the government's main 14 recommendations in the wake of the July 7 bombings. These were banning Hizb ut-Tahrir, automatically refusing asylum to anyone linked to terrorism anywhere in the world, making justification or glorification of terrorism anywhere an offence, and amending human rights laws to circumvent obstacles to new deportation laws.

Yesterday, an Acpo spokeswoman admitted police chiefs had "concerns" over these measures, but added that saying they opposed them was "too strong".